There are a number of thermal control problems which may arise in high heat flux environments, such as those encountered in air breathing engines, during hypersonic flight of aircraft, or in other non-aeronautical applications. The first problem concerns protecting the underlying airframe structure from destruction by the high heat flux via a thermal protection system (TPS). The other problem concerns controlling the temperature of a surface bounding a high velocity flow to a particular level, while that surface is simultaneously being subjected to high heat flux.
Back side cooling, film cooling, and transpiration cooling methods may all potentially deal with both problems in a single design, but may have significant drawbacks. For instance, they may require high coolant flow rates and may depend on the delivery of coolant to be cooled through a heavy, expensive, structural ducting and plenum system. A plenum may have to be provided directly behind any area which requires cooling. A further drawback of film cooling systems may be the expense associated with drilling large numbers of small holes in the surface to be cooled. Transpiration systems may be limited by the ceramic and sintered metal porous materials used for the surface to be cooled. Ceramics may be brittle and may lack structural strength when unsupported by a substrate. Sintered metals may be heavy and expensive.
Some of the prior ceramic foam TPS systems have the foam bonded to the structural member requiring cooling. Coolant may flow through the foam in the plane of the structural member being cooled so that the foam itself becomes the plenum for the cooling air. This method may work well as a TPS system, protecting the bond line with a much smaller amount of coolant than the traditional methods discussed above. However, achieving surface temperature control with this system may be difficult because the pressure loss in the coolant may become prohibitive at the coolant flow rates needed to maintain a given surface temperature.
Other prior art TPS systems may use ceramic foam bonded to a structural plenum. This system may provide good surface temperature control, and may also function as a TPS system. However, it may share a fundamental drawback with the traditional methods previously mentioned. Namely, it may employ a heavy, expensive, structural plenum for delivery of coolant to the surface.
A combined thermal protection and surface temperature control apparatus, and method for its manufacture and use, is needed which may solve or reduce one or more problems associated with one or more of the prior art apparatus.